This invention relates in general to beds and more particularly to patient support apparatus, including healthcare facility beds, having a wheel that can be deployed to contact a floor along which the patient support apparatus is being guided.
There is a continuing effort to improve the steering (e.g., tracking and maneuverability) of patient support apparatus (i.e., hospital beds, stretchers, and the like). Typically, such apparatus generally comprise castors (i.e., pivoting or swiveling wheels) located at four corners of the apparatus. Such apparatus are difficult to handle along straight paths because the axes of the castors are not maintained in a fixed relationship or orientation. Since the apparatus will tend to move in the direction of the rotation of a wheel, if the castors are pointed in different directions, the apparatus will be pulled in those respective directions, and therefore the apparatus will not have any fixed and predictable direction of motion. Additionally, it is difficult to steer or maneuver an apparatus on castors around corners because there is no fixed pivot axis for turning the apparatus. As a consequence, the person steering the apparatus must, through significant effort, force the apparatus to turn as desired. It is desirable that an operator be able to establish and maintain the path of motion of the apparatus.
To facilitate handling, the apparatus may include mechanisms to selectively brake one or more castors or to lock castors in a desired position after they have been manually adjusted to that position. Generally, because of the unpredictability of motion and the physical effort required to maneuver patient support apparatus, two people are often required to steer the apparatus.
In order to improve the tracking or maneuverability (e.g., the tendency of the apparatus to maintain an existing path of motion absent an operator force intended to cause the apparatus to deviate from the existing path of motion), it is known to deploy one or more additional wheels. For example, a deployable fixed axis auxiliary wheel may be located at the midpoint or center of the apparatus. This helps overcome the tendency of the apparatus to drift sideways while the apparatus is moved.